Method and system for providing fault recovery using composite transport groups

ABSTRACT

An approach is provided for performing fault recovery using composite transport groups (CTGs). A first logical channel is established within a composite transport group, wherein the first logical channel is established over a first link associated with a first service provider to a customer premise equipment (CPE) node configured to transport packets. A second logical channel is established within the composite transport group, wherein the second logical channel is established over a second link associated with a second service provider to an optical node. Packets are received over the first logical channel. Packets are received over the second logical channel if the first logical channel experiences a fault condition, wherein switching to the second logical channel is transparent to the CPE node.

BACKGROUND INFORMATION

Telecommunications networks have developed from connection-oriented,circuit-switched (CO-CS) systems, e.g., such as the public switchedtelephone network (PSTN), utilizing constant bit-rate, predefinedpoint-to-point connections to connectionless, packet-switched (CNLS)systems, such as the Internet, utilizing dynamically configured routescharacterized by one or more communication channels divided intoarbitrary numbers of variable bit-rate channels. With the increase indemand for broadband communications and services, telecommunicationsservice providers are beginning to integrate long-distance,large-capacity optical communication networks with these traditionalCO-CS and CNLS systems. Typically, these optical communication networksutilize multiplexing transport techniques, such as time-divisionmultiplexing (TDM), wavelength-division multiplexing (WDM), and thelike, for transmitting information over optical fibers. However, anincrease in demand for more flexible, resilient transport is drivingoptical communication networks toward high-speed, large-capacitypacket-switching transmission techniques, wherein switching andtransport functions occur in completely optical states via one or morepackets. Accordingly, as these optical communication networks continueto grow, there is an increasing need for telecommunication serviceproviders to develop fast failure recovery techniques to protect workingoptical communication paths from experiencing downtime as a result oflink and/or equipment failure.

Therefore, there is a need for an approach that provides packet-switchedoptical networks with efficient fault recovery techniques.

BRIEF DESCRIPTION OF THE DRAWINGS

Various exemplary embodiments are illustrated by way of example, and notby way of limitation, in the figures of the accompanying drawings inwhich like reference numerals refer to similar elements and in which:

FIG. 1 is a diagram of a system for providing fault recovery usingcomposite transport groups, according to an exemplary embodiment;

FIG. 2 is a diagram of an optical node configured to provide compositetransport groups, according to an exemplary embodiment;

FIG. 3 is a diagram of a composite transport group, according to anexemplary embodiment;

FIG. 4 is a flowchart of a process for routing network traffic viacomposite transport groups, according to an exemplary embodiment;

FIGS. 5A and 5B are, respectively, diagrams of a network traffic profileand a composite transport group status table, according to variousexemplary embodiments;

FIG. 6 is a flowchart of a process for fault recovery via compositetransport groups, according to an exemplary embodiment;

FIG. 7 is a flowchart of a process for fault recovery between autonomoussystems using composite transport groups, according to an exemplaryembodiment; and

FIG. 8 is a diagram of a computer system that can be used to implementvarious exemplary embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred apparatus, method, and software for providing fault recoveryusing composite transport groups are described. In the followingdescription, for the purposes of explanation, numerous specific detailsare set forth in order to provide a thorough understanding of thepreferred embodiments of the invention. It is apparent, however, thatthe preferred embodiments may be practiced without these specificdetails or with an equivalent arrangement. In other instances,well-known structures and devices are shown in block diagram form inorder to avoid unnecessarily obscuring the preferred embodiments of theinvention.

Although the various exemplary embodiments are described with respect tofault recovery on packet-switched optical transport networks, it iscontemplated that the various exemplary embodiments are also applicableto other equivalent transport networks, such as circuit-switched,burst-switched, label-switched, packet-switched, wavelength-switched,etc., networks.

FIG. 1 is a diagram of a system for providing fault recovery usingcomposite transport groups, according to an exemplary embodiment. Forthe purposes of illustration, a system 100 for providing fault recoveryamong client nodes (e.g., node 101) and one or more optical nodes (e.g.,optical nodes 103 and 105) using composite transport groups (CTGs) isdescribed with respect to packet-switched optical infrastructuresprovisioned by disparate service providers, e.g., service provider “A”and service provider “B.” In this manner, optical links 107 and 109 maybe considered “off-network” links (i.e., transport channels extendingbetween network 111 of service provider “A” and autonomous systems (AS)113 and 115 of service provider “B”), while optical link 117 may beconsidered an “on-network” link (i.e., a transport channel extendingbetween autonomous systems 113 and 115 of service provider “B”). It isnoted that the systems 113 and 115 can be sub-networks of a singleautonomous system, in an alternative embodiment. The client (subscriberor customer) nodes 101 are customer premise equipment (CPE), accordingto one embodiment, with the optical nodes 103 and 105 are under controlof the service provider, which in this instance is service provider “B.”Additionally, it is contemplated that the CPE node 101 can be owned bythe service provider. While specific reference will be made thereto, itis contemplated that system 100 may embody many forms and includemultiple and/or alternative components and facilities.

Traditionally, telecommunications service providers have implementedfault recovery techniques in optical communication networks via “1+1,”“1:1,” and “1:N” pathway protection schemes. Briefly, in “1+1” pathwayprotection, a transmitting node splits an optical signal (i.e., networktraffic) into two identical copies, such that each copy issimultaneously transmitted over two separate physical pathwaysestablished between transmitting and receiving nodes. Upon reception,receiving nodes monitor the quality of the two optical signals, andutilize the “better” of the two signals. If one pathway fails, thenreceiving nodes may receive data on the “other” pathway. In “1:1”pathway protection, optical signals are carried over a “working” pathwayonly, and in the event of working pathway failure, the optical signalsare switched over to a “backup” pathway by the transmitting andreceiving nodes. Since the backup pathway is only utilized duringworking pathway failure, then it is also possible to share the backuppathway between multiple working pathways, i.e., in “1:N” pathwayprotection. In any instance, however, multiple physical pathways must beestablished between transmitting and receiving nodes, whether or not thepathways are geographically dispersed. Nevertheless, given the fact thatmultiple physical pathways are required, “1+1,” “1:1,” and “1:N” pathwayprotection schemes represent expensive, bandwidth-inefficient techniquesfor fault recovery. It is apparent that improvements are needed.

Therefore, the approach according to certain embodiments stem from therecognition that by providing fault recovery through CTGs,telecommunications service providers can implement cost-effective,bandwidth efficient pathway protection. This is because CTGs manage setsof logical channels as “composite connections,” as well as associationsbetween client node instances and composite connections, which enableCTGs to dynamically distribute network traffic over the compositeconnections based on this information, as well as based on logicalchannel fault notification and composite connection status. In otherwords, CTGs, among other features, enable individual pathways to carrynetwork traffic from multiple client nodes, maintain independent pathwaytransport availabilities and capacities, and provide for disparatetransport rates, all the while enabling individual pathways to providepathway protection for one another.

According to one embodiment, system 100 provides fault recovery based onthe configuration of composite transport groups (CTGs) establishedbetween a client node 101, such as a client device, router, switch, orany other suitable customer premise equipment (CPE) (or Provider Edge(PE)), and two or more optical nodes, (e.g., optical nodes 103 and 105),such as a reconfigurable optical add/drop multiplexer (ROADM), or othersuitable optical transport platform (e.g., P-OTP (packet opticaltransport platform)). It is noted that the CTGs are configured toprovide connection-oriented, e.g., network traffic embodying, forexample, information packetized into one or more packets; furthermore,connectionless communications can be encapsulated within aconnection-oriented connection. In exemplary embodiments, one CTG (orcomposite connection) may be established for transport of networktraffic from client node 101 to optical node 103, and may include afirst set (or bundle) of logical channels (or component connections),while another CTG may be established for transport of network trafficfrom client node 101 to optical node 105, and may include a second setof logical channels. The first set of logical channels may include alogical channel defined by optical link 107 (e.g., a primary channel)and a logical channel defined by the conjunction of optical links 109and 117 (e.g., a secondary (or protection) channel). The second set oflogical channels may include a logical channel defined by optical link109 (e.g., a primary channel) and a logical channel defined by theconjunction of optical links 107 and 117 (e.g., a secondary channel). Itis contemplated; however, that logical channels may also be grouped inmultiple CTGs.

According to other embodiments, fault recovery may be implemented viaoptical nodes 103 and 105 based on the detection of a failure conditionrelating to one of the logical channels extending between client node101 and optical nodes 103 or 105, i.e., optical links 107 and 109.Failure conditions may stem from optical link failure and/or equipmentfailure. Moreover, the failure conditions may relate to either softfailures (i.e., performance degradation) or hard failures (i.e., total,or catastrophic failure). If a failure condition is detected, faultrecovery may be implemented transparently with respect to the clientnodes, e.g., client node 101, and can be performed based on theavailability of remaining logical channels associated with an affectedCTG. Namely, packets may be partially or wholly diverted from logicalchannels associated with the failure condition to logical channels thatare not associated with the failure condition. It is contemplated;however, that in those instances where affected logical channels areassociated with multiple CTGs, fault recovery measures can be performedamong the multiple CTGs.

Under the above arrangement, use of CTGs can save, for instance, up to50% access cost compared with traditional systems. This approach canprotect access service against any single link and card failure betweensite 111 and sites 113, 115. In addition, the service provider can savecarrier up to 50% on port costs. Further, customer provisioning can besimplified for the CPE node 101, ensuring link/card failure does notcause dramatic traffic pattern change.

The system 100 permits the CPE router/switch 101 to treat CTGs asphysical trunks. Instead of the CPE 101 re-routing traffic duringfailure conditions, the CTG handles the failure and re-routes thetraffic on its own. This preserves the configurations at the CPE 101;and the optical nodes 103, 105 (e.g., PE/P-OTP).

As seen in FIG. 1, system 100 includes networks 111, 113, and 115 that,in turn, include nodes 101, 103, and 105, respectively. In exemplaryembodiments, system 100 is a connection-oriented transport environmenthaving one or more optical links (e.g., optical links 107-109)established therein, wherein individual optical links embody opticalfibers configured to carry data between two nodes, e.g., between nodes101 and 103. It is noted that optical links 107, 109, and 117 may beautomatically setup and torn down by means of any suitable signalingprotocol. Accordingly, optical links 107, 109, and 117 may carryinformation over various wavelengths or “channels.”

Networks 113-115 may be any type of wired and/or wireless transportnetwork, such as a local area network (LAN), metropolitan area network(MAN), wide area network (WAN), etc. At least a portion of networks113-115 comply with the International TelecommunicationsUnion-Telecommunication (ITU-T) standards recommendation working draftG.800 titled, “Unified Functional Architecture of Transport Networks,”which is incorporated herein, by reference, in its entirety. Client node101 may be any suitable customer premise equipment, such as a computingdevice, router, switch, etc., while optical nodes 103 and 105 may be anysuitable optical transport platform, such as a terminal multiplexor, areconfigurable add/drop multiplexer, photonic switch, opticalcross-connect with optical-electrical-optical conversion, synchronousoptical networking cross-connect, signal regenerator, router, switch, orany other suitable optical networking interface, such as a packetoptical transport platform. In this manner, information transport canoccur between nodes 101-105 of networks 111-115 via optical links 107,109, and 117, which represent channels (or paths) along which packetsmay be transported. As such, a topology of system 100 can becharacterized via optical links 107, 109, and 117, which furthercharacterize the available transport capacity (e.g., bandwidth capacity)between nodes 101-105 of networks 113-115. Thus, during optical linkconfiguration, optical links 107, 109, and 117 may be established andgrouped into one or more CTGs for enabling fault recovery.

FIG. 2 is a diagram of an optical node configured to provide compositetransport groups, according to an exemplary embodiment. For descriptivepurposes, optical node 200 is described with respect to packetswitching; however, may include functionality for optical burstswitching, time division multiplexing (TDM), wavelength-divisionmultiplexing (WDM), etc. As shown, optical node 200 includes input linecards 201 a-201 n, output line cards 203 a-203 n, control interface 205,and optical switch section 207; however, it is contemplated that opticalnode 200 may embody many forms. For example, optical node 200 maycomprise computing hardware (such as described with respect to FIG. 8),as well as include one or more components configured to execute theprocesses described herein for providing fault recovery using compositetransport groups. Furthermore, it is contemplated that the components ofoptical node 200 may be combined, located in separate structures, orseparate physical locations. In other words, a specific topology is notcritical to embodiments of optical node 200 or system 100 for thatmatter.

According to one embodiment, input line cards 201 a-201 n act as “n”input interfaces to optical node 200 from “n” transmitting nodes (e.g.,client node 101), while output line cards 203 a-203 n act as “n” outputinterfaces from optical node 200 to “n” destination nodes (e.g., opticalnodes 103 and 107). When packets arrive at optical node 200, input linecards 201 a-201 n port packets to receiving interface 209 of opticalswitch section 207. Receiving interface 209 separates headers andpayloads from individual packets. Header information is provided tocontrol interface 205 for routing purposes, while payloads are switchedto destination output line cards 203 a-203 b via hybrid switching fabric211 and sending interface 213. That is, hybrid switching fabric 211routes payloads to appropriate pathways on sending interface 213,whereby updated headers are combined with switched payloads. Thecombination is output to destination nodes via output line cards 203a-203 n.

In particular implementations, control interface 205 is configured toprovision one or more logical channels through hybrid switching fabric211 based on system 100 topological information provided to controlinterface 205. These logical channels can be grouped into one or moreCTGs. According to one embodiment, control interface 205 establishes theaforementioned CTGs for transport of network traffic from client node101 to optical node 103, and from client node 101 to optical node 105.

Thus, by grouping one or more logical channels (or componentconnections) into a CTG, networks can achieve transportation resilienceover composite connections, which route network traffic transparentlyfrom transmitting and receiving nodes. FIG. 3 is a diagram of acomposite transport group, according to an exemplary embodiment. Asshown, composite connection 301 is made available via CTG 303, whichincludes one or more parallel component connections (e.g., physicaland/or logical links), e.g., component connections 305 a-305 m, sharingsimilar ingress and egress points.

Accordingly, and from the perspective of CTG 303, each componentconnection 305 a-305 m acts as an independent transportation entity, andtherefore, enables independent transportation path availabilities forcomposite connection 301, i.e., for network traffic. That is, if networktraffic (e.g., a number of packetized messages) is sequenced at ingressand transported over one or more component connections (e.g., componentconnection 305 a-305 m), then the network traffic may or may not arriveat egress in the same sequential order. Thus, when information istransported via composite connection 301 utilizing CTG 303, a layerprocessor (LP) at ingress (e.g., LP 307) distinguishes componentconnections 305 a-305 m by processing each packet and distributing thepackets over composite connection 301 via one or more of componentconnections 305 a-305 m. The ability of LP 307 to distinguish betweencomponent connections 305 a-305 m is dependent upon packet header formatand information encoded therein. Thus, if a particular componentconnection (e.g., component connection 305 a) fails, LP 307 isconfigured to utilize reserved bandwidth capacity in the “other”component connections (e.g., component connections 305 b-305 m) totransport network traffic, i.e., LP 307 reroutes network traffictransparently from the entity attempting to transport the traffic. Inthis manner, a network gains transport resilience via compositeconnections 301 because individual component connection failures areautomatically resolved via the remaining operational componentconnections, and the transportation entities are only privy to the factthat composite connection 301, as a whole, is operational.

Thus, composite connection 301 made available via CTG 403 can be appliedin both connection-less packet-switched (CL-PS) optical networks, aswell as in connection-oriented packet-switched (CO-PS) optical networks.In CL-PS environments, component connections 305 a-305 m can exist aspoint-to-point links between autonomous systems (e.g., autonomoussystems 113 and 115). Optical nodes 103 and 105 utilize informationencoded in packet headers provided by, for example, client nodes (e.g.,node 101) to distinguish between client communications. That is, theprocessing entity (e.g., control interface 205) of optical nodes 103 and105 utilizes this information to differentiate between componentconnections (e.g., component connections 305 a-305 m) and distributenetwork traffic over one or more CTGs (e.g., CTG 303). Thus, networktraffic transported via CTG 303 is “seen” by client nodes (e.g., node101) as “belonging” to composite connection 301, as opposed to theparticular component connection 305 a-305 m “actually” supporting thetransport of network traffic.

In CO-PS environments, component connections 305 a-305 m of CTG 303 canbe configured as point-to-point links, as above, or as point-to-pointpaths. Paths may be established over one or more optical links (e.g.,optical links 107, 109, and/or 117) and, thereby, traverse one or morenodes (e.g., nodes 101-105). For composite connection 301 to supportmultiple communications from client nodes (e.g., node 101) informationmay be encoded within individual packet headers to differentiate betweencommunications. Accordingly, at composite connection 301 ingress, LP 307can use this information to distribute packets over componentconnections 305 a-305 m, which enables multiple composite connections301 to be configured over a CTG, such as CTG 303. Further, LP 307 may,when determining which component connection to utilize to supporttransport, use this information to perform traffic engineering androuting processes, e.g., to assign resource capacity or priority forindividual communications, etc. In particular embodiments, thisinformation may be acquired from a network management system (notshown), as opposed to the packet headers. Thus, a composite connection301 may be traffic engineered per component connections 305 a-305 m, aswell as traffic engineered based on component connection attributes,e.g., bandwidth capability, operational status, and the like, or node101 attributes, e.g., allocated capacity, origination address,destination address, etc. Particular client node attributes andcomponent connection attributes are described with respect to FIGS. 5Aand 5B.

As previously mentioned, system 100 utilizes logical channels (orcomponent connections) over one or more CTGs for information transport,which allows for transport resilience given the independent transportavailability of several component connections being grouped as a CTGand, thereby, forming a composite connection.

FIG. 4 is a flowchart of a process for routing network traffic viacomposite transport groups, according to an exemplary embodiment. Forillustrative purposes, process 400 is described with reference to FIGS.1 and 3. It is noted that process 400 assumes the existence of one ormore previously established (or constructed) physical connections (e.g.,optical links 107, 109, and 117) configured to transport networktraffic, such as user information or network control information. Thesteps of process 400 may be performed in any suitable order or combinedin any suitable manner.

At step 401, one or more optical nodes (e.g., optical nodes 103 and 105)configure one or more component connections (i.e., logical channels)based on a topology of system 100, i.e., based on the establishment ofone or more physical connections (e.g., optical links 107, 109, and117). Individual component connections may be configured over an opticallink (e.g., optical link 107) or over a group of optical links (i.e., apath), such as a path defined by optical links 109 and 117. In thismanner, component connections are independent channels configured fortransporting information, wherein each component connection isindividually characterized by its own transport availability, i.e.,existence, maximum bandwidth, and operational status. Thus, in step 403,various component connections may be grouped into one or more CTGs, suchthat any given CTG (e.g., CTG 303) includes several parallel componentconnections (e.g., component connections 305 a-305 m) establishing atransport route from a desired point “A,” e.g., node 101, to a desiredpoint “B,” e.g., optical node 103. For example, system 100 may becharacterized by two CTGs, e.g., one CTG may embody optical link 107(i.e., a physical component connection) and the conjunction of opticallinks 109 and 117 (i.e., a logical component connection or a path), andthe second CTG may embody optical link 109 and the conjunction ofoptical links 107 and 117. The characteristics of a composite connection(or CTG) may be stored to a memory (not shown) of, for example, opticalnodes 103 and 105 and/or any other suitably accessible repository (notshown) of system 100. According to one embodiment, the CTGcharacteristics may be stored to one or more profiles (or tables) ofinformation, such as network traffic profile and/or CTG status table 550optical nodes 103 and 105 may route network traffic over one or moreCTGs (e.g., CTG 303), per step 405. That is, network traffic, such aspacketized optical signals, can be transported over one or morecomponent connections (e.g., component connection 305 a-305 m), whichare defined by one or more optical links (e.g., optical links 107, 109,and 117).

FIGS. 5A and 5B are, respectively, diagrams of a network traffic profileand a CTG status table, according to various exemplary embodiments.Network traffic profile 500 provides network traffic visibility so as toenable optical nodes 103 and 105 the ability to maximize and efficientlyallocate available bandwidth among various information transportingnodes, e.g., node 101, based on, for instance, component connectionavailabilities. In essence, profile 500 aids in the design,implementation, and maintenance of quality of service (QoS) by providingknowledge of one or more traffic instances. As shown, profile 500provides categories for client node 501 (i.e., devices transportinginformation over, for example, system 100), allocated capacity 503(i.e., amount of bandwidth provisioned to corresponding client nodes),assigned CTG 505 (i.e., CTG “currently” supporting corresponding clientnode traffic), assigned component link 507 (i.e., correspondingcomponent connection of the CTG supporting corresponding client nodetraffic), and utilized bandwidth 509 (i.e., a “current” consumption ofallotted bandwidth by client nodes). It is noted, however, that networktraffic profile 500 may include any other suitable network trafficparameter, such as administrative cost, capacity reduction factor,holding priority, over-subscription factor, path bandwidth requirement,placement priority, etc.

Moreover, CTG status table 550 can provide system overview information,i.e., an accounting of the transport availabilities of one or more CTGs,as well as the component connections associated therewith. As such,table 550 also enables optical nodes 103 and 105 to maximize andefficiently allocate bandwidth, as well as dynamically distributenetwork traffic upon network failure notification, such as a componentconnection going “out-of-service.” In essence, table 550 aids in faultmanagement and recovery by providing knowledge of the status of thecomponent connections. According to one embodiment, table 550 includescategories for CTGs 551 (i.e., macro accounting of available transportlinks), load 553 (i.e., macro accounting of the “current” amount ofbandwidth transported via corresponding CTGs), component connection 555(i.e., micro accounting of available transport links associated withcorresponding CTGs), load 557 (i.e., micro accounting of the “current”amount of bandwidth being transported via corresponding componentconnections), maximum bandwidth 559 (i.e., total bandwidth capability ofcorresponding component connections), and status (i.e., “current”operational state of component connections). It is noted, however, thatCTG status table 550 may include other suitable parameters. Further,profile 500 and table 550 may be grouped or otherwise divided.

Accordingly, system 100 can provide for transport resilience uponfailure conditions, such as link failure or equipment failure. That is,CTGs enable system 100 to dynamically distribute network traffic basedon component connection fault notification, component connection status,and/or client node bandwidth allowances and demands. It is noted thatthese failure conditions may be soft (i.e., performance degradation) orhard (i.e., total, or catastrophic failure).

FIG. 6 is a flowchart of a process for fault recovery via compositelinks, according to an exemplary embodiment. For illustrative purposes,process 600 is described with reference to FIG. 3. It is noted that thesteps of process 600 may be performed in any suitable order or combinedin any suitable manner. At step 601, LP 307 detects component connectionfailure on, for example, component connection 305 a ingress, andgenerates failure detection message for transmission over an adjacentcomponent connection, e.g., component connection 305 b, i.e., on aforward path. Accordingly, LP 307 transmits failure detection messagetowards component connection 305 a egress via component connection 305b, in step 603. Once component connection 305 a egress receives failuredetection message, LP 309 generates fault notification message andtransmits fault notification message towards component connection 305 aingress via component connection 305 b, i.e., on a reverse path. In thismanner, LP 307 receives fault notification message from LP 309 andtransfers it to component connection 305 a ingress, per step 605.According to certain embodiments, fault notification messages arecontinually or periodically provided until component connection 305 a isrepaired. As such, component connection 305 a ingress marks, per step607, component connection 305 a as “out-of-service” via LP 307, upon ahard failure. When the failure is soft, component connection 305 aingress maintains component connection 305 a as “in-service,” butprovides a capacity reduction factor for limiting the amount of networktraffic supported by the degraded connection. The capacity reductionfactor may be utilized to reduce, for example, the maximum bandwidth 559of affected component connections. In either instance, this informationis recorded in, for example, CTG status table 550 maintained in, forinstance, a memory (not shown) of LP 307 or another suitably accessiblememory or repository (not shown) of system 100. Thus, at step 609, LP307 routes all network traffic among “in-service” componentconnection(s), e.g., component connections 305 b-305 m, based on one ormore parameters of the CTG status table 550. Hence, compositeconnections 301 enable network traffic to be restored quickly andefficiently, without requiring client nodes (e.g., client node 101) tobe reconfigured for rerouting transmissions, which can be a timeconsuming and costly.

During step 611, LP 307 continues to monitor the state (e.g., faultstatus) of component connection 305 a ingress, such as in a continuous,periodic, or “on-demand” fashion. If the failure is not recovered, LP307 continues to route network traffic over “in-service” componentconnections, i.e., component connections 305 b-305 m, based onavailability and capacity to support network traffic. Once the failureis recovered, component connection 305 a ingress stops receiving faultnotification messages, and marks, via LP 307, component connection 305 aas “in-service” or updates maximum bandwidth 559, either of which isrecorded in component connection status table 550, per step 613. After,for instance, the duration of a predetermined recovery time, LP 307 maythen reroute network traffic among the various “in-service” componentconnections, i.e., component connections 305 a-305 m.

Accordingly, because LP 307 is privy to information concerning networktraffic instances and CTG statuses, composite connections 301 enable LPs(e.g., LP 307) to perform dynamic network traffic distributions based onthe status and capacity of the various component connections. Further,CTGs allow grouped component connections (e.g., component connections305 a-305 m) to protect one another, instead of requiring additionalphysical connections, i.e., additional optical links, to be constructed.Thus, if one component connection fails (whether soft or hard), affectednetwork traffic may be redistributed to one or more of the unaffectedcomponent connections within a composite link, whereas in a conventionalsystem network traffic would be required to be provisioned on a separate“protection” path, i.e., an optical link provided in the case of primaryoptical link failure, which inefficiently expends resources. Ifcomponent connections are grouped to more than one CTG, then multipleCTGs can take action to recover and redistribute network traffic,whereas in conventional systems, only the “protection” paths may beutilized. Furthermore, if multiple component connections fail (whethersoft or hard), network traffic may still be redistributed based on thestatus and capacity reduction factor of the component connections;however, if both the primary and protection paths of a conventionalsystem fail (whether soft or hard), then network traffic cannot resumeuntil one of the paths is repaired.

FIG. 7 is a flowchart of a process for fault recovery between autonomoussystems using composite transport groups, according to an exemplaryembodiment. For illustrative purposes, process 700 is described withreference to FIG. 1. In step 701, optical nodes 103 and/or 105 establishfirst and second logical channels between two autonomous systems, e.g.,network 111 and the conjunction of autonomous systems 113 and 115, aspart of a CTG. For example, optical node 103 may provision, via anysuitable signaling protocol, a first logical channel over optical link107, and a second logical channel over the conjunction of the opticallinks 109 and 117. In this manner, optical node 103 and 105 may utilizethe first logical channel as a primary logical channel (e.g., a workingchannel) and the second logical channel as a secondary logical channel(e.g., a protection channel). Thus, during step 703, network traffic(e.g., packets) originating at client node 101 for optical node 103 willbe routed between the autonomous systems via the first logical channel.At step 705, however, optical node 103 detects a failure conditionaffecting the first logical channel, such as a hard optical link failureto optical link 107. Based on the failure detection, optical node 103updates network traffic profile 500 and/or CTG status table 550, suchthat the network traffic can be routed to the second logical channeltransparently from client node 101, per step 707. Namely, client node101 still “thinks” network traffic is routed via the macro CTG; however,a disparate logical channel (i.e., the second logical channel) istransporting the network traffic between the autonomous systems, insteadof the first logical channel. Accordingly, the CTG saves serviceprovider “B” substantial resources, as only one primary off-networkoptical link must be provisioned between network 111 and autonomoussystems 113 and 115 (i.e., optical links 107 and 109), wherein pathprotection is achieved for these off-network optical links via anon-network optical link (e.g., optical link 117) extending betweenautonomous systems 113 and 115. Further, bandwidth is not unnecessarilywasted via a separate projection path because the protection pathdescribed herein is also provisioned as a primary path within anotherCTG for the transport of network traffic between client node 101 andoptical node 105. It is noted that the steps of process 700 may beperformed in any suitable order or combined in any suitable manner.

The processes described herein for providing fault recovery usingcomposite transport groups may be implemented via software, hardware(e.g., general processor, Digital Signal Processing (DSP) chip, anApplication Specific Integrated Circuit (ASIC), Field Programmable GateArrays (FPGAs), etc.), firmware or a combination thereof. Such exemplaryhardware for performing the described functions is detailed below.

FIG. 8 illustrates computing hardware (e.g., computer system) 800 uponwhich an embodiment according to the invention can be implemented. Thecomputer system 800 includes a bus 801 or other communication mechanismfor communicating information and a processor 803 coupled to the bus 801for processing information. The computer system 800 also includes mainmemory 805, such as a random access memory (RAM) or other dynamicstorage device, coupled to the bus 801 for storing information andinstructions to be executed by the processor 803. Main memory 805 canalso be used for storing temporary variables or other intermediateinformation during execution of instructions by the processor 803. Thecomputer system 800 may further include a read only memory (ROM) 807 orother static storage device coupled to the bus 801 for storing staticinformation and instructions for the processor 803. A storage device809, such as a magnetic disk or optical disk, is coupled to the bus 801for persistently storing information and instructions.

The computer system 800 may be coupled via the bus 801 to a display 811,such as a cathode ray tube (CRT), liquid crystal display, active matrixdisplay, or plasma display, for displaying information to a computeruser. An input device 813, such as a keyboard including alphanumeric andother keys, is coupled to the bus 801 for communicating information andcommand selections to the processor 803. Another type of user inputdevice is a cursor control 815, such as a mouse, a trackball, or cursordirection keys, for communicating direction information and commandselections to the processor 803 and for controlling cursor movement onthe display 811.

According to an embodiment of the invention, the processes describedherein are performed by the computer system 800, in response to theprocessor 803 executing an arrangement of instructions contained in mainmemory 805. Such instructions can be read into main memory 805 fromanother computer-readable medium, such as the storage device 809.Execution of the arrangement of instructions contained in main memory805 causes the processor 803 to perform the process steps describedherein. One or more processors in a multi-processing arrangement mayalso be employed to execute the instructions contained in main memory805. In alternative embodiments, hard-wired circuitry may be used inplace of or in combination with software instructions to implement theembodiment of the invention. Thus, embodiments of the invention are notlimited to any specific combination of hardware circuitry and software.

The computer system 800 also includes a communication interface 817coupled to bus 801. The communication interface 817 provides a two-waydata communication coupling to a network link 819 connected to a localnetwork 821. For example, the communication interface 817 may be adigital subscriber line (DSL) card or modem, an integrated servicesdigital network (ISDN) card, a cable modem, a telephone modem, or anyother communication interface to provide a data communication connectionto a corresponding type of communication line. As another example,communication interface 817 may be a local area network (LAN) card (e.g.for Ethernet™ or an Asynchronous Transfer Model (ATM) network) toprovide a data communication connection to a compatible LAN. Wirelesslinks can also be implemented. In any such implementation, communicationinterface 817 sends and receives electrical, electromagnetic, or opticalsignals that carry digital data streams representing various types ofinformation. Further, the communication interface 817 can includeperipheral interface devices, such as a Universal Serial Bus (USB)interface, a PCMCIA (Personal Computer Memory Card InternationalAssociation) interface, etc. Although a single communication interface817 is depicted in FIG. 8, multiple communication interfaces can also beemployed.

The network link 819 typically provides data communication through oneor more networks to other data devices. For example, the network link819 may provide a connection through local network 821 to a hostcomputer 823, which has connectivity to a network 825 (e.g. a wide areanetwork (WAN) or the global packet data communication network nowcommonly referred to as the “Internet”) or to data equipment operated bya service provider. The local network 821 and the network 825 both useelectrical, electromagnetic, or optical signals to convey informationand instructions. The signals through the various networks and thesignals on the network link 819 and through the communication interface817, which communicate digital data with the computer system 800, areexemplary forms of carrier waves bearing the information andinstructions.

The computer system 800 can send messages and receive data, includingprogram code, through the network(s), the network link 819, and thecommunication interface 817. In the Internet example, a server (notshown) might transmit requested code belonging to an application programfor implementing an embodiment of the invention through the network 825,the local network 821 and the communication interface 817. The processor803 may execute the transmitted code while being received and/or storethe code in the storage device 809, or other non-volatile storage forlater execution. In this manner, the computer system 800 may obtainapplication code in the form of a carrier wave.

The term “computer-readable medium” as used herein refers to any mediumthat participates in providing instructions to the processor 803 forexecution. Such a medium may take many forms, including but not limitedto non-volatile media, volatile media, and transmission media.Non-volatile media include, for example, optical or magnetic disks, suchas the storage device 809. Volatile media include dynamic memory, suchas main memory 805. Transmission media include coaxial cables, copperwire and fiber optics, including the wires that comprise the bus 801.Transmission media can also take the form of acoustic, optical, orelectromagnetic waves, such as those generated during radio frequency(RF) and infrared (IR) data communications. Common forms ofcomputer-readable media include, for example, a floppy disk, a flexibledisk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM,CDRW, DVD, any other optical medium, punch cards, paper tape, opticalmark sheets, any other physical medium with patterns of holes or otheroptically recognizable indicia, a RAM, a PROM, and EPROM, a FLASH-EPROM,any other memory chip or cartridge, a carrier wave, or any other mediumfrom which a computer can read.

Various forms of computer-readable media may be involved in providinginstructions to a processor for execution. For example, the instructionsfor carrying out at least part of the embodiments of the invention mayinitially be borne on a magnetic disk of a remote computer. In such ascenario, the remote computer loads the instructions into main memoryand sends the instructions over a telephone line using a modem. A modemof a local computer system receives the data on the telephone line anduses an infrared transmitter to convert the data to an infrared signaland transmit the infrared signal to a portable computing device, such asa personal digital assistant (PDA) or a laptop. An infrared detector onthe portable computing device receives the information and instructionsborne by the infrared signal and places the data on a bus. The busconveys the data to main memory, from which a processor retrieves andexecutes the instructions. The instructions received by main memory canoptionally be stored on storage device either before or after executionby processor.

While certain exemplary embodiments and implementations have beendescribed herein, other embodiments and modifications will be apparentfrom this description. Accordingly, the invention is not limited to suchembodiments, but rather to the broader scope of the presented claims andvarious obvious modifications and equivalent arrangements.

1. A method comprising: establishing a plurality of composite transportgroups among a customer premise equipment (CPE) node, a first opticalnode, and a second optical node, wherein the composite transport groupsprovide transport of packets from the CPE node to either the firstoptical node or the second optical node, and each of the compositetransport groups includes a plurality of logical channels arranged overoff-network links from the CPE node to the first optical node and thesecond optical node and an on-network link between the first opticalnode and the second optical node; detecting a failure condition relatingto one of the logical channels between the CPE node and the firstoptical node, the one logical channel being associated with one of thecomposite transport group; and routing the packets, transparent to theCPE node, over another one of the logical channels of the one compositetransport group.
 2. A method according to claim 1, wherein the onelogical channel is designated as a primary channel and the other logicalchannel is designated as a secondary channel.
 3. A method according toclaim 1, wherein the first optical node and the second optical node arereconfigurable optical add/drop multiplexers.
 4. A method according toclaim 1, wherein the one composite transport group includes a firstlogical channel defining a connection path from the CPE node to thefirst optical node, and a second logical channel defining a connectionpath from the CPE node to the second optical node and then the firstoptical node.
 5. A method according to claim 1, wherein the CPE node isa router.
 6. A method according to claim 1, wherein the failurecondition stems from either a link failure or equipment failure.
 7. Amethod according to claim 1, wherein the first optical node and thesecond optical node are controlled by a common service provider.
 8. Amethod according to claim 1, wherein the first optical node is a part ofa first autonomous system and the second optical node is a part of asecond autonomous system.
 9. A system comprising: a first optical nodeconfigured to communicate with a customer premise equipment (CPE) nodeover an off-network link; and a second optical node configured tocommunicate with the CPE node over another off-network link and tocommunicate with the first optical node over an on-network link, whereina plurality of composite transport groups are defined among the CPEnode, the first optical node, and the second optical node, wherein thecomposite transport groups provide transport of packets from the CPEnode to either the first optical node or the second optical node, andeach of the composite transport groups includes a plurality of logicalchannels arranged over the off-network links from the CPE node to thefirst optical node and the second optical node and the on-network linkbetween the first optical node and the second optical node, wherein thefirst optical node is configured to detect a failure condition relatingto one of the logical channels between the CPE node and the firstoptical node, the one logical channel being associated with one of thecomposite transport group, wherein the packets are routed, transparentto the CPE node, over another one of the logical channels of the onecomposite transport group.
 10. A system according to claim 9, whereinthe one logical channel is designated as a primary channel and the otherlogical channel is designated as a secondary channel.
 11. A systemaccording to claim 9, wherein the first optical node and the secondoptical node are reconfigurable optical add/drop multiplexers.
 12. Asystem according to claim 9, wherein the one composite transport groupincludes a first logical channel defining a connection path from the CPEnode to the first optical node, and a second logical channel defining aconnection path from the CPE node to the second optical node and thenthe first optical node.
 13. A system according to claim 9, wherein theCPE node is a router.
 14. A system according to claim 9, wherein thefailure condition stems from either a link failure or equipment failure.15. A system according to claim 9, wherein the first optical node andthe second optical node are controlled by a common service provider. 16.A system according to claim 9, wherein the first optical node is a partof a first autonomous system and the second optical node is a part of asecond autonomous system.
 17. A method comprising: establishing a firstlogical channel within a composite transport group, wherein the firstlogical channel is established over a first link associated with a firstservice provider to a customer premise equipment (CPE) node configuredto transport packets; establishing a second logical channel within thecomposite transport group, wherein the second logical channel isestablished over a second link associated with a second service providerto an optical node; receiving packets over the first logical channel;and receiving packets over the second logical channel if the firstlogical channel experiences a fault condition, wherein switching to thesecond logical channel is transparent to the CPE node.
 18. A methodaccording to claim 17, further comprising: establishing anothercomposite transport group to define a primary logical channel and asecondary logical channel to another CPE node.
 19. A method according toclaim 17, wherein the optical node is reconfigurable optical add/dropmultiplexer.
 20. An apparatus comprising: logic configured to establisha first logical channel within a composite transport group, wherein thefirst logical channel is established over a first link associated with afirst service provider to a customer premise equipment (CPE) nodeconfigured to transport packets, wherein the logic is further configuredto establish a second logical channel within the composite transportgroup, the second logical channel being established over a second linkassociated with a second service provider to an optical node; and aninterface configured to receive packets over the first logical channel,wherein the interface is further configured to receive packets over thesecond logical channel if the first logical channel experiences a faultcondition, wherein switching to the second logical channel istransparent to the CPE node.
 21. An apparatus according to claim 20,wherein the logic is further configured to establish another compositetransport group to define a primary logical channel and a secondarylogical channel to another CPE node.
 22. An apparatus according to claim20, wherein the optical node is reconfigurable optical add/dropmultiplexer.